1. Field of the Invention
The present invention relates to an insulating resin composition and/or a transparent insulating resin composition, and more particularly, it relates to a resin composition suitable for screen printing to use in a thin-film type electronic device, as well as to a resin composition for constituting an insulating film for use in a thin-film type electronic device.
The present invention also relates to a solar cell comprising the resin composition above.
2. Description of the Prior Art
In a thin-film type electronic device (i.e., an electronic device constructed by principally stacking thin films) such as a thin-film solar cell, various types of resin compositions have been studied for forming an insulating film for use as an interlayer dielectric film in a multilayered structure or an insulating film in a multi-level crossed interconnection.
The resin composition above should possess insulating properties for use as an interlayer insulating film, adhesion to the upper and the lower layers, weathering resistance, moisture resistance, heat resistance, wear resistance, scratch resistance, flexibility, surface hardness, applicability of an ink by means of screen printing and the like, and hardenability.
Studies have heretofore been made on thermosetting, thermoplastic, and ultraviolet (UV) curable resin compositions such as styrene resins, saturated polyester resins, unsaturated polyester resins, epoxy resins, alkyd resins, silicone resins, acrylic resins, and fluororesins. Details of the studies are described in, for example, JP-A-61-218625 (the term "JP-A-" as referred to herein signifies an "unexamined published Japanese patent application").
However, in spite of the above proposed resin compositions above, a resin composition which satisfies the requirements with good balance between the requirements is yet to be developed.
Particularly, in a multilayered structure comprising stacked thin films such as that in a solar cell or similar thin-film type electronic device with an interlayer insulating film or an insulating film for multi-level crossed interconnections, none of the known resin compositions was found to satisfy the required characteristics enumerated above as well as printability of an ink, hardenability of the printed film, and productivity. Accordingly, no resin composition developed heretofore is suitable for use as an interlayer insulating film or an insulating film for multi-level crossed interconnections.
Furthermore, an extensive study has been made of resin encapsulates for thin-film electronic devices, especially resin compositions that form a transparent protective film on the surface of a solar cell of thin-film structure.
The resin compositions for such use need not only transparency but also many characteristic properties required of a protective film (such as weather resistance, moisture resistance, heat resistance, wear resistance, scratch resistance, flex resistance, surface hardness, and adhesion to the substrate and the thin film). It also needs good printability when used in the form of an ink for screen printing.
Conventional resin compositions for transparent protective films are formed from a variety of thermoplastic and thermosetting resins and UV-curing resins, such as styrene resin, saturated polyester resin, unsaturated polyester resin, epoxy resin, silicone resin, acrylic resin, and fluoroplastics. Their detailed descriptions will be found in Japanese Patent Publication No. 17342/1988 and Japanese Patent Laid-Open Nos. 69874/1981 and 218625/1986.
However, none of the conventional resin compositions meet the requirements for the above-mentioned characteristic properties. Especially when used as a transparent protective film on solar cells of thin film structure, they are not satisfactory in transparency, properties required of a protective film, printability as an ink, curability, and productivity.